VHF marine radio is the most popular way of communicating with other vessels and shore stations where the range allows. VHF sets are simple, compact, robust units and, compared to other two-way communication devices, inexpensive.
Radio waves travel in straight lines, which means that 'if you can see it, you can talk to it'.
So providing there's nothing in the way, like the curvature of the earth or a land mass to deflect it or stop it altogether, range will depend on the respective heights of the transmitting and receiving vhf marine antenna.
On land, coastguards and harbour masters will have theirs at the top of their buildings.
On a sailboat there's only one sensible place to fit it; at the top of the mast.
Here's a useful table which will give you a reasonable idea of the range of your particular installation.
The first number is the height of the VHF antenna above sea level in metres (m), and the second is the distance to the horizon in nautical miles (nm).
So if your sailboat has its VHF antenna mounted 15m above sea level and another vessel has its 10m above sea level, then you can just about communicate with each other providing you're no more than 18 nautical miles (10nm + 8nm) apart.
If you were communicating with a shore station with its VHF antenna 100m above sea level, then your VHF range would be 36 nautical miles.
Similarly your handheld VHF (2m above sea level) would only have a 12 nautical mile range when communicating with a vessel with its VHF antenna 10m above sea level.
Range is also affected by power, which is measured in watts. Fixed installations can be switched between low power (1w) and high power (25w). For longer range marine communication, you'll need an SSB radio installation.
Until fairly recently, coastguard stations worldwide and all vessels at sea were required to keep a listening watch on VHF channel 16 (156.8MHz) and 2182kHz. Vessels in distress relied on their MAYDAY call being picked up and acted upon as a result of their vigilance.
All this has now changed with the advent of DSC equipped VHF radios, which automate the whole process at the press of a distress activation button.
Most of us opt for one of these located at our boat's navigation area, with extension speaker mounted in the cockpit.
After many years of reliable service, my ICOM VHF rolled over and died, and I decided to replace it with a Standard Horizon combined VHF/DSC/AIS set.
Coupled to my chart-plotter it displays AIS data of all appropriately equipped vessels on the display.
They're obviously a little more expensive than a standard set, but a lot cheaper than two individual VHF and AIS sets. It's proved to be a great purchase.
All cruising boats should carry a handheld VHF marine radio in addition to the fixed installation - ideally a waterproof one that floats like the ones shown here. But why?
Imagine you're going ashore in the yacht's tender in a brisk offshore wind...
The outboard stops or you drop an oar. Without a handheld VHF set to call for help on, you could well find yourself in a spot of bother; particularly so if darkness is setting in.
And if, like these, it has a built-in GPS receiver you can tell your rescuers exactly where you are.
A handheld VHF radio is a very useful back-up if the fixed VHF set lets you down.
Hand-held sets normally have power settings of 2.5w and 5w, and some models are now available with DSC (Digital Selective Calling).
If you buy a marine VHF radio in the UK today it will have channels 1 to 28 and 60 to 88. Channels 29 to 36 and 38 to 59 are private channels that you won't have access to. Channel 37 is numbered as 'M' and is used by UK marinas and yacht clubs, along with Channel 80.
Channel 16 is reserved for Initial Calling and for Distress and Safety Calling. Having established contact via Channel 16 in a non-distress situation, the station called will nominate a Working Channel to which both parties will switch for the rest of their communication.
The Working Channels are 06, 08, 09, 10, 13, 15, 17, 67, 69, 72, 73 and 77. Channels 10, 67 and 73 are also used by the UK Coastguard so it's best to avoid these. Channel 70 is reserved solely for DSC (Digital Selective Calling) only.
Note that in this case 'International' doesn't include the United States and Canada; they use different VHF channels 'over there'.
In the UK you're required by law to have both a Ship Radio License and a VHF/DSC (Short Range) Operators Certificate.
The Ship Radio Licence is free but is required for all VHF marine radios. You can get a Ship Radio Licence right here...
The VHF/DSC (Short Range) Operators Certificate licenses the operator to use the VHF marine radio. You must not send general transmissions on VHF without one. You'll need to attend (and pass) a VHF course to get your hands on one of these.
The VHF Marine Radio Course operated by the RYA is one of the most popular ones, covering:~